| ObjectiveVitamin D, also known as antirachitic vitamin, not only maintains bone health, but also plays an important role in body metabolism. It has been reported that vitamin D deficiency is associated with the development of tumor, autoimmune diseases, obesity, diabetes and cardiovascular diseases. This research studied healthy adults living in Yangguang community of Jinan, assessed vitamin D status of this population and explored the correlations of serum vitamin D levels with obesity, fasting blood glucose, blood pressure and lipids. Subjects and methods1. Subjects (1) One thousand eight hundred sixty five individuals who aged20to82years were participated in our research from October2009to November2009. All participants were urban residents living in Yangguang community of Jinan (36°N) more than five years.1277urban adults, with strict inclusion criteria and exclusion criteria, were selected in the present analysis which explored the relationship between serum vitamin D levels and the parameters of obesity and body fat.(2) After excluding subjects with high hypertention or dyslipidemia, intakes of anti-hypertension or lipid-lowing drugs and the missing data,1244adults selected from the above study population were included to analyze the relations of serum vitamin D levels with fasting blood glucose (FBG), insulin resistance index (HOMA-IR) and insulin secretion index (HOMA- β) and further discussed the associations with serum vitamin D levels and blood pressure and lipids.2. Clinical data Venous blood samples were collected after overnight fasting for eight hours from all subjects. The serum levels of calcium, phosphorus, creatinine, alanine aminotransferase, fasting blood glucose, insulin (INS), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG) and serum uric acid (UA) were measured by automatic biochemical analyzer. The serum vitamin D [25(OH)D] concentrations were determined by enzyme immunoassay. A specially trained professional person measured the anthropometric parameters of all the subjects such as height, weight, waist circumference (WC) and hip circumference. Meanwhile, body mass index (BMI) and waist to hip ratio (WHR) were calculated. Body fat, body fat percentage and waist fat to hip fat ratio were measured by body composition analyzer. Systolic and diastolic blood pressure was measured by ohm of dragon electron sphygmomanometer after all participants sitting for at least five minutes. The information such as history of disease and medication was carefully noted down.3. Statistical analyses Data analyses were performed using SPSS18.0. All data were expressed as mean±standard error (SE) for continuous variables that were normally distributed, median for continuous variables that were not normally distributed, number or percentage for categorical variables. The abnormal distribution variables were applied to analyze the data after log transformation. An independent t test, single factor variance analysis or chi-square test was used to compare the difference between the groups. In data analysis, various statistic methods, such as simple correlation analysis, partial correlation analysis, multivariate liner regression analysis and bivariate logistic regression analysis, were used to explore the associations of serum levels of25(OH)D with indexes of obesity and body fat, fasting blood glucose, blood pressure and lipids.Results1. The distribution of vitamin D status among1277subjectsThe mean age was46.32±0.41years old and32.73%were males. The mean serum25(OH)D value of the study subjects was40.41±0.33nmol/L. Nearly77percent of the subjects had vitamin D deficiency and four percent were severely deficient. Males had higher serum25(OH)D levels than females and the average levels of25(0H)D were42.47±0.61nmol/L and39.40±0.39nmol/L, respectively.2. The relationship between serum25(OH)D levels and obesity indexes and body fat parameters among1277subjectsAfter adjustment for age and gender by partial correlation analysis, serum25(OH)D levels were significantly and inversely related to BMI (r=-0.057, P=0.042), WC (r=-0.084, P=0.003) and WHR (r=-0.099, P <0.001), body fat (r=-0.073, P=0.009), body fat percentage (r=-0.072, P=0.010) and waist fat to hip fat ratio (r=-0.107, P<0.001).In multivariable stepwise liner regression analysis, the levels of25(OH)D were negatively associated with WC (w=-0.080, P=0.015) and WHR(β=-0.123, P<0.001), but not with BMI (β=-0.033, P=0.277). When body fat, body fat percentage and waist fat to hip fat ratio were separately entered into multivariable regression models, serum25(OH)D levels were negatively correlated with these three body fat indexes (P <0.05for all). However, when these three body fat parameters were included in the same model, only waist fat to hip fat ratio remained significant association with serum25(OH)D levels (P=-0.131, P=0.001).The results of covariance analysis showed that abdominal obesity subjects had higher serum25(OH)D levels than the counterparts grouped by WC or WHR (P<0.05), but there was no significant difference in serum25(OH)D levels between the non-obesity group and the general obesity group grouped by BMI.3. The association between serum levels of25(OH)D and fasting blood glucose in1244subjectsIt was showed that the serum levels of fasting blood glucose was decreased as the serum25(OH)D levels increased by covariance analysis. When adjusting for the confounding factors, such as age, gender, drinking status and so on, serum25(OH)D level was significantly and inversely related to FBG (r=-0.086, P=0.002) and positively associated with Log HOMA-β (r=0.079, P=0.005), whereas no significant correlation was found between log HOMA-IR and serum25(OH)D. The results of bivariate logistic regression analysis showed the levels of serum25(OH)D were inversely related to impaired fasting glucose(OR=0.974,95%CI:0.955-0.992, P=0.006).4. The relationships of serum25(OH)D levels with blood pressure and lipids in1244subjectsSerum25(OH)D levels were inversely associated with Log TG (β=-0.058, P=0.016) by multiple regression analysis, but no association was observed serum25(OH)D and SBP、DBP、TC、LDL-C and HDL-C. However, the results of bivariate logistic regression analysis showed serum25(OH)D levels were not associated with hypertriglyceridemia, hypercholesterolemia, high LDL-C, low HDL-C, and hypertension(P>0.05). ConclusionsOur study found that the prevalence of vitamin D deficiency was very common in healthy adults of Yangguang community in Jinan. Abdominal body fat accumulation was independently related to decreased vitamin D levels. Serum vitamin D levels were inversely associated with the occurrence of impaired fasting glucose, but not with hypertension and dyslipidemia. |
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